1. Field of the Invention
The invention relates to an apparatus and a method for regulating the temperature of a substrate and in particular for regulating the temperature of a wafer.
2. Description of the Related Art
Holding apparatuses and in particular wafer chucks, which mostly have a planar bearing surface for the wafer-type substrates, are customarily used for testing circuit arrangements on wafer-type substrates, such as semiconductor wafers, for example. It is necessary for a large number of electrical measurements for testing a substrate to adjust the temperature of the substrate to a constant predetermined value and/or to maintain it at a constant predetermined value.
For this purpose, heating and/or cooling elements are formed in a substrate holding apparatus or the holding apparatus is combined with a conventional thermochuck. In order to transfer the regulated temperature of the apparatus also to the substrate, the substrate must be in good thermal contact with the bearing surface of the holding apparatus. To this end, in conventional substrate holding apparatuses vacuum openings, for example, are formed in the contact surface in order to enable the substrate to be sucked up. Conventional substrate holding apparatuses are provided with a closed cooling circuit in which a cooling fluid circulates through ducts in the substrate holding apparatus to a heat exchanger and back again to the substrate holding apparatus. Since a closed circuit only comprises a fixed, non-expandable volume, it may be possible depending on the cooling fluid at relatively high operating temperatures that high pressures occur in the circuit such that the substrate holding apparatus and/or parts of the cooling circuit are subjected to high stresses. Consequently, the risk of failure increases and, for example, the seals in the circuit must in conventional appliances be designed to be particularly resistant to pressures, which incurs corresponding expenses. Moreover, appliances of this type regularly need to be serviced which involves a high degree of complexity.
It is an object of the present invention to provide an inexpensive and reliable regulation of the temperature of substrates and in particular of semiconductor wafers, wherein desired changes in temperature can be carried out quickly and precisely.
The object is achieved by virtue of the features of the independent claims. Preferred embodiments are the subject matter of the dependent claims.